Abrasive products and methods of manufacturing the same



Patented Mar. 15, 1938 UNITED STATES 2,111,006 .rrica ABRASIVE PRODUCTS METHODS OF MANUFACTURING THE SAME Norman P; Bobie, Niagara Fa N. Y., a ssignor a) the Carborundum Company, Niagara Falls, .N. Y., a corporation of Dellare N Drawing.

Application December 10, 1936, Serial No. 115,191

15 (oi. sr-asc) This invention relates to abrasive products and methods of manufacturing the same. More specifically, the invention lsconcerned with abrasive products such as polishing setup, wheels; grinding wheels and abrasive paper and cloth in the preparation of which there is employeda binder comprising an aqueous solution ordispersion of a vinyl compound which is either soluble or selfdispersible in water.

This application is a continuation-in-part of my copending applications Serial No. 746,849,

generated. Glue is, also unsatisfactory in that.

' it putrefies, hydrolyzes and loses strength when sive and sometimes toxic.

stored in a liquid'condition. condensation products are open to objection in that the-phenolic resins are inherently brittle,

poorly adhesive and'require heat to harden them sufi'lciently to permit handling. Furthermore, the

use of these resins involves the employment of solvents which are expensive, frequently explo- In order to develop strength in heat hardenable resins it is necessary to subject the resin to heat treatment. Since coated abrasives and polishing wheels are commonly made with ,cellulosic backing materials such as cloth and paper which are weakened when heated, this characteristic of phenolic resins presents afurther disadvantage to their use in making coated abrasives. Many such resins also contain free phenol which reacts with certain fibers commonly used in cloth or paper and'further weakens the backing material. Further, certain phenolic resins penetrate the fibers and on curing embrittle them, making them more susceptible to breaking.

I have discovered that certain polyvinyl compounds of the general nature of gums that are water-soluble or self-dispersible in water are excellent binders in cementing abrasive particles to each otherand to backings.

In general, I have found that polymerized vinyl compounds, which contain sufficient hydroxyl (OH), carboxy (COOI-D' or neutralized carboxy groups (C'OOR, where R represents K, Na, NH4, etc.) in the urolecule, are either water-soluble or 'self-dlspersible in water and that such materials are strongly adhesive, tough, and highly satisfactory binders for attaching abrasive grains to a backing or to eachother in the production of abrasive articles. I have further found that these water-soluble or self disperslble gums, by

virtue of theirhydroxy and carboxy groups, may

Phenol aldehyde be advantageously reacted with materials such as phenolic resins-containing free aldehyde, aldehydes such as benzaldehyde, formaldehyde, tannic acid, chromic acid'and other chromium compounds, 012, Bra and sulphur or other hardening or insolubilizing agents in the preparation of certain classes of abrasive products. This reactlon is preferably brought about after the abrasive products have been formed in order that the binder may be water-soluble while the articles are being formed;

. These compounds may be prepared in a num ber of ways and may be one of several classes of polymerized vinyl compounds such as vinyl alcohol, esters, ethers and acetals.

Furthermore, materials having widely difie'rent properties may be made by varying the method of preparation. It is therefore possible by the use of my invention to provide binders having difierent properties but having the common advantage thatthey are all adapted to be Hous fled by water, and hence are inexpensively applied to a backing.

One specific material or rather one group of materials which I have found to be very well adapted for use in making abrasive articles comprises the class wherein the hydroxyl group is attached directly to the vinyl group. The sim plest form of such material is polyvinyl alcohol.

Referring further to this class of materials, the binder may comprise the 'polymerizedalcohol alone or it may contain both an alcohol and other vinyl compounds such asa polyvinyl ester. ,Al-

ternatively bodies comprising vinyl compounds which have been only partially hydrolyzed and are therefore what might be called partial alcohols may be employed.

A third class of materials which I have found suitable for use as binders for abrasive articles comprises the reaction product of polyvinyl alcohol with an acid or an aldehyde containing hy-' droxyl groups or the chemical equivalents thereof. Examples: of such compounds are the vinyl ester of lactic or tartaric acid or the reaction product of polyvinyl alcohol with a hydroxy aldehyde. l

Still other classes of water-dispersible or watersoluble polymerized vinyl compounds include certain vinyl others, such as vinyl methyl ether or -ethers formed, for example, 'by the reaction of polyvinyl alcohol with alkylene oxides; partial vinyl esters of dibasic acids containing uncombined carboxyl (COOH) groups; partially chlorinated polyvinyl alcohol containing uncombined hydroxyl groups; and'copolymers of polyvinyl alcohol with vinyl methyl ether.

Furthermore, for some purposes, these watersoluble or self-dispersible compounds may be advantageously modified by the incorporation of other binders which are water-soluble, such as c v I glue, methyl cellulose, polyvinyl methyl ether, certain polymerized acrylic compounds, or sodium silicate, miscible with water in their initial state such as certain phenol-aldehyde and urea- .aldehyde condensation products, or colloidally dispersed such as aqueous dispersions of rubber including rubber latex.

Glue is commonly used in manufacturing coated abrasives but has the disadvantage that it is brittle. Mixtures of glue and various watersoluble vinyl compounds have been found to be very valuable because the vinyl gums are naturally tough and thus compensate for and reduce the brittleness of glue. Mixtures of water-soluble polyvinyl compounds with phenol-aldehyde condensation products which may contain an excess of phenol or aldehyde, have also been found to be especially well adapted for use as a binder for coated abrasives for use in some kinds of abrading, as for example in metal surfacing. Alternatively, polyvinyl alcohol may be dissolved in phenol followed by subsequent reaction with an aldehyde.

Some of these water-soluble vinyl compounds, such as polyvinyl alcohol, may also be mixed with other liquid adhesives which are not soluble in water by employing the polyvinyl compound as a colloidal dispersing agent which stabilizes suspensions of water-insoluble resins in water' and promotes the formation of colloidal aqueous dispersions or emulsions.

My new adhesives have the tremendous advantage in making coated abrasives over other binders which are not soluble in water in that they can be readily applied in the conventional abrasive paper making machine which is commonly designed to handle solutions of glue. Since such apparatus and methods are well known in the art, it appears to be unnecessary to describe them 'in detail. It is, therefore, to be understood that aqueous solutions or dispersions of my binder may be applied to the backing and subsequently coated with abrasive grains in any of the manners well known to the art. Methods which are commonly usedare completely described in a publication of the Canadian Department of Mines No. 699 (Part IV, Artificial Abrasives and Maniactured Abrasive Products and Their Uses).

In making coated abrasives I have sometimes found it advantageous to use my adhesive alon with other adhesives. For example, in certain cases I prefer to adhere the grain layer to the backing, using hide glue and to apply my aqueous vinyl adhesive to the'grain coating as a size coat ing. This sizing coating may be rolled orsprayed on according to the usual methods. In other cases I use my aqueous vinyl adhesive for adhering the grain coating to the backing and then apply a sizing coating of phenolic resin or other adhesive tothe abrasive.

Some of the binders used in my invention form viscous solutions at comparatively low concentrations. Since the solid content of the liquid adhesive is an importantiactor in the manufacture of coated abrasives, it is desirable that this be as high as possible. I have foundthat the viscosity of solutions of my improved binders can be materially reduced by incorporating, with concentrated gels of the binder, certain peptlzing agents. For example, many substituted hydrazines may be incorporated with a viscous gel'and the mixture given an aging treatment at a somewhat elevated temperature. A specific treatment which I have used successfully consists of incorporating a few per cent of the zinc chloride air-mos double salt of phenyl hydrazine in finelydivided form into an aqueous gel of polymerized vinyl alcohol, and heating the mixture in a closed container in the presence of asubstantlal proportion of air at 210 F. for about 24 hours. 7

I will now describe my invention by a number of specific examples. It is to be understood that these examples are for illustrative purposes only and are not limitative.

Example I 'a result of the formation of polyvinyl alcohol,

which is insoluble in organic solvents. The gel then shrank exuding an anhydrous solution of methyl acetate in methyl alcohol which was drawn from the container. i

The mass of gel continued to release liquid in reduced amounts as time went on, and at the end of an additional 96 hours about two-thirds of the original volume of solvent mixture had separated.

The mass of gel, which was at-this stage some-.

What-of a cheesy consistency, was then cut up into pieces, dissolved in water, and heated to remove the remaining solvent mixture.

The aqueous solution of the gelled material was applied to a backing of paper of a type commonly used in the production of coated abrasives and known as lb. cylinder paper, abrasive grains were distributed 'over the adhesive coated surface of the backing and the article was warmed to remove the water from the resin solution.

An additional or sizing coat of the adhesive was then applied in the conventional manner and the article was again heated to thoroughly dry the adhesive. I

The abrasive product was formed into a belt and proved to be highly eflicient in' surfacing wood.

Example I] The product prepared as in Example I was admixed with a glue solution formed by swelling 1 part of hide glue in 2 parts of water and warming. The solution of the gel and the glue solu-, tion were mixed in proportions to give a solid content .of 60 parts of gum to 40 parts of dry glue.

Example III The syrupy liquid thus obtained, which was a partially hydrolyzed acetate, or partial alcohol,

was used as an adhesive for coated abrasives in the manner described in detail in Example 1.

Example IV A partial alcohol was prepared as described in Example III except that polyvinyl acetate which had been previously reacted with a small percent- F. for 8 hours,'at the end of I,

I 2,111,0oe age of acetaldehyde was substituted for the unmodified polyvinyl acetate of Example III.

Example V Polyvinyl alcohol was prepared as described in Example I and was then esterified with lactic acid and taken up in water. Theaqueous liquid was then applied to a backing material and an 50 polyvinyl alcohol solution.

abrasive coated article was made as described in detail in Example I.

Example 171 Polyvinyl alcohol was prepared by dissolving 216 pounds of polyvinyl acetate in 465 pounds of anhydrous methanol, adding a catalyst made by dissolving 80 grams of metallic sodium in 8 liters of methanol, and allowing the mixture-to stand until a gel of the polyvinyl alcohol had formed.

The gum so prepared was then dissolved in water to form a.20% solution and this solution was mixed with a normally liquid phenol-formalde hyde condensation product in proportions such that the liquid adhesive contained equal parts of polyvinyl alcohol and phenolic condensation product.

tendency to separate.

Cloth drills after presizing were coated with the liquid adhesive'and with fused alumina abrasive grains in a'regular abrasive cloth making machine and after a preliminary drying to remove water from the adhesive coating, the articles wereadditionally coated with a second or siz-.

ing layer of the adhesive.

The thus-coated' articles were dried at room temperature for two hours and were then heat treated for hours at 250 F. The finished product was found to be'especially efiicient for use in abrading ferrous metals. I

In place of the normally liquid phenol-formaldehyde condensation products I may use other resins in liquid form such as ammonia solutions of alkyd resins, aqueous solutions of the initial condensation product of urea and formaldehyde, solutions of solid phenolic resins, drying oilmodified resins, and liquid alkyd resins.

Example VII Sections comprising many'pieces of muslin stitched together were sized on the sides with After the sections had dried they were glued togetherwith polyvinyl alcohol and clamped to form a ,wheel 16" in diameter by 2 face. trued on a lathe and was sized with polyvinyl alcohol.

The face of the wheel was then brushed with a t 10% polyvinyl alcohol solution and was rolled in warm 60 grit fused alumina polishing grain.

This coating wasdried slightly and a second coat ing ofpolyviny'l alcohol adhesive and abrasive applied.

The wheel-was then dried in'a dry atmosphere at 100'F. a.nd finally at 212? F. The wheel was mounted on a polishing stand and operated at a speed of 7000 surface feet per minute polishing steel.

The polyvinyl alcohol used for the adhesive was produced from a polyvinyl acetate having a relatively high molecular weight. It was very tough and fairly flexible. 1

N Exam le vrrr A paste was made comprising. fused "alumina polishing-grain and asolutio'n 'of polyvinyl alcohol The mixture was a viscous homogeneous liquid which was stable and showed no The face of the .wheel was on coarse grits.

in water'in the proportions of 90 parts grain to 10 parts solid polyvinyl alcohol. This paste'vv as' applied to the face ofa sized 'p'olishing'wheel prepared for coating as in Example VII. The coated wheel was dried, mounted and used as in the previous example.

Example IX No. 16 mesh fused alumina was wet with a hot 20% solution of polyvinyl alcohol and dried. The

dried mass was crushed and screened through 10 mesh. These coated granules were recoated with 20% polyvinyl alcohol solution and dried. The mass was crushed and screened through a 6 mesh screen. Thescreened coated grain-was wetwith a little 20% polyvinyl alcohol solution hot and the mixture cold pressed to shape. The .pressed article was dried over night at. 250 F. The total bond present in the bonded abrasive was 10.9%.

Example X r A plasticizing liquid was made as follows:

75 parts polyvinyl alcohol solution 28.6% solid in water i i parts normally liduid heat reactive phenolic condensation product resin.

This plasticizing mixture was added to 14 grit fused alumina in the proportion of 90 parts to 850 parts of abrasive. 150 parts of powdered A- stage phenolic resin was added and uniformly mixed in to give free flowing resin coated compound and a binder of v another class, it is possible to produce articles which are particular:

1y well suited for special kinds of abrading. The

After moistening with a little properties of the abrasive product may also be varied by using vinyl compounds which have been polymerized to difierent degrees whereby the molecules of the polymers contain different numbers of monomeric molecules. In general, I have found that the higher polymers are more satisfactory for most purposes, although the invention is not limited to the use of the more highly polymerized materials. V

As indicated above, my invention has many advantages over the adhesives formerly used in the manufacture of abrasive articles. It provides a method for making abrasives with'binders of different properties and therefore makes it possible to produce such articles which are particularly efficient for specific purposes. For example,

coated abrasives which are to be usedfor wood,- working require'a binder having different properties than where the article is to'be used for working steel. Furthermore, the characteristic of the binder can be varied depending upon the grit size of the abrasive grains which areto be used. Where coarse grits are employed, the bind er must be stronger and tougher because the,

force applied to the binder through the abrasive grains isgreater/ i'n such cases than where finer grits are used, by reason or the greater leverage In addition, my improved binders have the advantage over glue and normally liquid phenolic resins that aqueous solutions or dispersions of the binders are stable and adapted to be kept in'liquid condition without deterioration. As is known,,

glue solutions putrefy upon standing and the strength and adhesiveness of the glue are impaired by subjection to temperatures substantially above 60 F. Consequentlyzwhere glue is employed as an adhesive, as in the manufacture of coated abrasive products, fresh batches of glue must be made up daily and precautions must be taken in the handling of the glue, both in its liquid state and after it has been applied to the backing to be' sure that it is not overheated. Liquid phenolic resins also deteriorate with age even at normal temperatures, becoming much thicker in viscosity and unsuitable for use. At temperatures above normal this thickening and solidification becomes much more rapid. My binders may be heated to comparatively high temperatures without affecting the properties of the binder and are therefore more readily solidified and dried than is glue.

As has been pointed out; the binders are ob- .tainable in various degrees of toughness and flexibility, depending upon the degree ,of polymerization of the product and are further adapted to be modified by the inclusion of suitable modifying agents.

Furthermore, my new adhesives have been found to be well adapted for use in the preparation of setup wheels because the adhesives 'can be liquefied and sold in liquid condition either alone or admixed with the abrasive grain, since there is no danger of putrefaction. Where glue is used,

, the user must prepare the glue solutions and in i to many instances is neither equipped nor trained to utilize glue to the best advantage.

As indicated, my invention is further adapted to a number of modifications such as the inclusion of other liquid adhesives whichare miscible with the aqueous polyvinyl adhesives, or inert filling materials such as powdered flint, and in general to the modifications commonly used in the art, such as the incorporation of plasticizing or fiexibilizing agents or other modifiers. The liquefied binders may be incorporated with the abrae sive grainsby the methods described in the specific examples or by other suitable methods. For example, certain of the liquefied binders have been found to be especially adapted for spraying and have been applied as sizing coats for coated abrasives by this method. 1

Other modifications of the invention may be employed and the invention maybe embodied in other methods and forms than those specifically described, such as abrasive discs, where the binder may be employed to attach the abrasive grains to a backing (which may include vulcanized fiber) or to attach a preformed article to a backing such as steel, a hardened plastic material, wood or the like. It is therefore to be understood that the scope of the invention is not to be determined by; the specific illustrations herein given butby the appended-claims. I

I claim:

' 1. An abrasive article comprising abrasive grains and a solidified binder comprising a polymerized vinyl compound containing sufiicient hydroxyl groups to be self-dispersible in water.

-2. An abrasive article comprising abrasive amines grains and a solidified binder comprising the reaction product of a hardening agent with a polymerized vinyl compound containing sumcient hydroxyl groups to be self-dispersibie in water.

3. A bonded abrasive article comprising abrasive grains bonded into a unitary article with a binder comprising a polymerized vinyl compound containing sufiicient hydroxyl groups to be selfdispersible in water. 1

4. A coated abrasive article comprising a backing material and a layer of abrasive grains attached thereto by a binder comprising a polymerized vinyl compound containing suflicient hydroxyl groups to be self-'dispersible in water.

5. A coated abrasive article comprising a backing material and a layer of abrasive grains attached thereto by a binder comprising polyvinyl alcohol.

6. A coated abrasive article comprising a backing material and a layer of abrasive grains attached thereto by a binder comprising a partially hydrolized polyvinyl compound.

7. A coated abrasive article comprising a. backing material and a layer of abrasive grains attached thereto by a binder comprising a polymerized vinyl ester of a. hydroxy acid.

8. A coated abrasive article comprising a backing material and a layer of abrasive grains attached thereto by a binder comprising a polyvinyl compound containing sufiicient hydroxyl groups to'be self-dispersible in water, and a watersoluble adhesive substantially free from the vinyl group.

9. A coated abrasive article comprising a backing material and a layer of abrasive grains attached thereto by a binder comprising glue and a polymerized vinyl compound containing sufiicienthydroxyl groups to be self-dispersible in water.

'19. A flexible abrasive article comprising a flexible base, abrasive grains, and a bond for securing said abrasive grains to said base, said bond comprising polyvinyl alcohol and a plasticiz'er therefor.

11. A flexible abrasive article comprising a I flexible base, abrasive grains and a-bond for securing said abrasive grains'to said base, said bond comprising polyvinyl alcohol and a polyhydroxy compound as a plasticizer therefor.

12., An abrasive article comprising abrasive grains and a solidified binder comprising the reaction product of an aldehyde with a polymerized vinyl compound containing sufiicient hydroxyl groups to be self-dispersible in water. 13. An abrasive article comprising abrasive grains and a solidified binder comprising the reaction product of a chromium compound with a polymerimd vinyl compound containing suflicient hydroxyl groups to be self-dispersible in water.

14. An abrasive article comprising abrasive grains and a solidified binder comprising a heathardened reaction product of a heat-hardenable condensation product and a polymerized vinyl compound containing sufficient hydroxyl groups to be self-dispersible in water.

' 15. An abrasive article comprising abrasive grains and a solidified binder comprising the heat-hardened product of a heat-hardenable phenolic condensation product and a. vinyl compound containing sufiicient hydroxyl groups to be self-dispersible in water. 1

- NORMAN P. ROBIE. 

